Method of synthesizing isopentane hydroperoxide

ABSTRACT

In the synthesis of an alpha diolefin (exemplified by isoprene) involving the hydroperoxidation of a saturated hydrocarbon (such as, isopentane with molecular oxygen), the improvement in yield of the hydroperoxide by the addition to the hydroperoxidation reactor of a tertiary alcohol (e.g. 2-methyl 2-butanol).

United States Patent [191 Dubois et a1.

[ Dec. 17, 1974 METHOD OF SYNTHESIZING ISOPENTANE HYDROPEROXIDE [75] Inventors: Claude Dubois, Martigues; Jean Maurin, Seine Maritime, both of France [73] Assignee: Compagnie Francaise de Raffinage,

Paris, France [22] Filed: Mar. 25, 1971 [21] Appl. No.: 127,958

[30] Foreign Application Priority Data Mar. 27. 1970 France 70.11121 [52] US. Cl. 260/6l0 B, 260/617 H [51'] Int. Cl. C07c 73/06 [58] Field of Search 260/610 B, 617 H [56] References Cited UNITED STATES PATENTS Fisher 260/604- 2,845,461 7/1958 Winkler et a]. 260/610 B 2,862,973 12/1958 Winkler et a1. 260/610 B 2,843,633 7/1958 Natta et al. 260/610 B 3,360,584 12/1967 Kollar 260/610 B 3,523,976 8/1970 Reni et a1. 260/610 Primary Examiner-Bernard Helfin Assistant ExaminerW. B. Lone Attorney, Agent, or Firm-Curtis, Morris & Safford 5 7 ABSTRACT 3 Claims, 3 Drawing Figures 1 METHOD OF SYNTHESIZING ISOPENTANE I HYDROPEROXIDE The present invention relates to a method for the hydroperoxidation of isopentane by action of a gas containing molecular oxygen, whether or not diluted in an inert gas. More particularly, it relates to an improvement in said method.

Isopentane hydroperoxide is an intermediate product in the manufacture of isoprene from isopentane and methyI-Z-butylene. It is a highly desired monomer because of the elastomers to which it is a precursor upon homopolymerization or copolymerization with other monomers.

In the above-indicated method of manufacturing isoprene, isopentane hydroperoxide serves, in the presence of a suitable catalyst such as molybdenum naphthenate, to oxidize methyl-2-butylene into methyl 2,3- butanediol or into methyl 2,3-epoxy butane, depending upon whether the reaction is carried out in the presence or absence of water. The diol or epoxide then leads to isoprene by dehydration.

The ordinary method used to effect the synthesis of isopentane hydroperoxide consists in reacting molecular oxygen with isopentane in liquid phase. The hydroperoxidation is carried out under pressure at a temperature generally between 100 and 200C. Good contact between the liquid and the gas is assured by any suitable means. This general technology is disclosed inapplicants coworkers applications, Ser. Nos. 30,276, 34,172, and 40,278.

It is found that by this method it is impossible to obtain an isopentane conversion of more than per cent without a substantial increase in the production of the byproducts, such as, Z-methyl 2-butanol, acetone, ethanol and acetic acid.

An object of the present invention is toimprove the selectivity of such a reaction for isopentane hydroperoxide in the synthesis of this compound.

The applicants have found that the addition of certain substances to the reaction medium increases the yield of isopentane hydroperoxide for a given isopentane conversion rate.

The present invention concerns, therefore, a method of synthesizing isopentane hydroperoxide by action of molecular oxygen, whether or not diluted in an inert gas, on isopentane in liquid phase. Specifically, the hydroperoxidation reaction is carried out in the presence of'an amount of tertiary alcohol equal to between 0.75 per cent and 15 per cent of the total number of gram molecules constituting the liquid reaction medium.

The present invention concerns the isopentane hydroperoxide prepared by the disclosed method.

The tertiary alcohols generally used in the present invention are: tertiary butyl alcohol, 2-methyl Z-butanol, Z-methyl Z-pentanol, and 3-methyl S-pentanol. Other tertiary alcohols may be used; for example, 2-phenyl Z-propanol.

In a batch method of preparation of isopentane hydroperoxide, the tertiary alcohol is introduced into the reactor before initiating the reaction in an amount, expressed in gram molecules of between 0.75 per cent and 15 per cent and, preferably, 075 and 8. per cent of the isopentane introduced.

In a continuous method tertiary alcohol is maintained in the reactor at a substantially constant amount of between 0.75 per cent and 15 per cent and, preferably,

' cules of the liquid components of the reaction medium.

The applicants have found that the addition of tertiary alcohol to the reaction medium not only increases the yield of isopentane hydroperoxide and reduces the yield of Z-methyl 2-butanol, but also, even more unexpectedly, reduces the yields of acetone and acetic acid for a given isopentane conversion rate.

The total amount of by-products of the hydroperoxidation produced is, therefore, decreased. Moreover, it has been found that under certain conditions practically no tertiary alcohol is consumed at all in the reaction, contrary to what would occur if a secondary alcohol were introduced into the medium.

Among the tertiary alcohols which can be used, 2- methyl Z-butanol is particularly advantageous since it constitutes one of the by-products of the hydroperoxidation of isopentane.

When isopentane hydroperoxide is subsequently con- 1 tacted with an olefin, having at least four carbon atoms so as to give rise to the diol or the epoxide which are the precursors of the diolefin of the same carbon structure as the olefin, 2-methyl Z-butanol, which comes from the reduction-of the isopentane hydroperoxide, may advantageously be separated from the reaction medium and used as additive in the synthesis of the iso-- pentane hydroperoxide.

In this specification and the accompanying drawings, we have shown and described in preferred embodiments of our invention and have suggested various alternatives and modifications thereof; but it is to be understood that these are not intended to be exhaustive and that many other changes and modifications can be made within the scope of the invention. These suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will thus be enabled to modify it and embody it in a variety of forms, each as may be best suited to the conditions of a particular use.

In the accompanying drawings:

FIG. 1 is a diagram showing the application of the method of the present invention to the preparation of methyl-2,3-butanediol.

FIG. 2 is a graph indicating the variation in the yield of isopentane hydroperoxide produced, expressed in per cent gram molecules of converted isopentane, as a function of the conversion rate of the isopentane.

FIG. 3 is a graph indicating the variation in the yield of compounds having the carbonyl function, expressed in per cent gram molecules of converted isopentane as a function of the conversion rate of the isopentane (in the method of preparing isopentane hydroperoxide).

A specific embodiment of the present invention will now be described with reference to FIG. 1, illustrating the preparation of methyl 2,3-butanediol, which leads to isoprene by dehydration.

Isopentane 2-methyl 2-butanol and air are introduced into a hydroperoxidation reactor 1 through the lines 2, 3, and 4, respectively. The reaction is carried out under pressure at a temperature close to C and with vigorous agitation of the medium. The reaction productsare removed through the line 5 and introduced into a flash distillation column 6 where the iso pentane is removed via line 7 and recycled. The other products, consisting primarily of isopentane hydroperoxide, are discharged through the line 8, which feeds the oxidation reactor 9. Water and methy1-2-butylene l and 11, respectively. The catalyst used in this reactor may be, for example, molybdenum naphthenate.

A pressure of 9 bars of pure oxygen is established in the autoclave, and the liquid is agitated by means of an oscillating cradle device; The temperature is gradually brought to 150C and maintained at this value. A con- The reaction temperature is about 120C. The reaction W tfllal Pressure of 31 l5 mainlallled y P products are introduced through the line 13 into a dislzmgfllth Pure Pxygem The f reacuon 'F tillation column 14 at the top of which the unreacted gg b l cofnvefslon rate" It vanes methyl-2-butylene is collected through the line 12 and tween f b an 9 mmutes or i g utmverslon recycled. Line 15, extending from the column 14, feeds h 0 etween per Cent an per cen respeca distillation column 16, from the top of which acetone, me a by product is eliminated through line 17 At the end of the test, the autoclave 1S cooled rapidly O The other components pass out through line 18 and to rooms tsg zgg fi z g gig' zlz g s gg g l pass into yet another distillation column 19. The head y jj a S q p fractlon passing through the line primarily l5 The tests were carried out with conversion rates of of z'methyl It a comams byproducts between 9 and 18 per cent. The results of these tests such as, methyl isopropyl ketone and traces of water. are repmsen-ted by Curve A in FIG 2 and Curve C in A part of this fraction is recycled into the isopentane FIG 3 I hydr operoxidation reactor through the line 3, while the Curvev A represents the variation of the yield of {3:22 5 f i a gii izz i gg g l if 20 droperoxide (expressed in percent gram molecules of y y y converted isopentane) as a function of the isopentane to the oxidation reactor 9. The dehydration reactor and Conversion rate (expressed in per Cent gram molecules the recycling of the methyl 2-butylene have not been of isopentane introduced) shown in FIG 1. The products discharged through the Curve C shows the variation of the yield of lme 22 contain primarily methyl 2,3-butanediolwh1ch, 25 pounds having the carbonyl function (primarily after removal of h trace? of catalyst and l tone) as a function of the isopentane conversion rate. Such "F' proyldes lsoprene by Catalync In order to draw the curves, the averages of the valhydration. It IS important not to recycle thr traces of ues of the numerous measurements made were used acetic acid into the reactor 1 via the line 20 and then the line 3. This would have a harmful effect on the iso- EXAMPLE ll pentan? hydlopeloxldatlon Q This is an example illustrating the method of the presl mvemlon fllrthermoreylllustfatefl by the ent invention wherein 2-methy1 2-butanolis added to lowing examples, which are not limitative in character. the reaction medium The manner of Operation is in an EXAMPLE other respects identical to that described in Example I. The 2-methyl 2-butanol is introduced at the same time The tests described In this example were carried out as the isopentane in an amount f between 1 and 8 per without adding tertiary alcohol to the react on medium. Cent f the number f gram molecules f isopentane They are given in order to permit comparislons with the troduced. method of the lnvemlon- The manner of Operation The tests were carried out with conversion rates of scribed below will not be changed in the other exam- 40 between 9 d 18 per Cent, plesl The results obtained are represented by Curve B in One starts from refinery isopentane. Pu y FIG. 2 for the yield ofisopentane hydroperoxide and by tillation, having an isopentane content by weight of C v D i FIG, 3 f r the ield of compounds having 96.8 per cent. The main impurities are normal pentane th -b f cti n, (1.5 per cent), normal butane (0.98 per cent), and Collected in Table I are several measurements, inmethyl butylene (0.48 per cent). eluding those which were made in order to draw Curves i TABLE I Test I II In IV V VI VII VIII 2-methy1 Z-butanol introduced 0.75 1 2 2 4 8 8 l2 converted isopentane 16.5 14.3 16.0 11.1 12.3 10.0 16.6 9 .8 yields of isopentane hydroperoxide 60.0 67.0 65.0 79.2 71.9 79.3 65.2 77 .5 yield of compounds havtigg :18 car ny function 30.0 27.5 28.0 24.7 25.2 25.0 28.0 25.l

Points representative of these measurements have been set forth in FIGS. 1 and 2. The number of the corresponding test shown, in parenthesis. beside each point.

B and D. In this table are set forth in successive order the following values:

the amount of 2-methyl Z-butanol introduced (ex;

isopentane introduced); and

the yields of isopentane hydroperoxide and of compounds having a carbonyl function (expressed in per cent gram molecules ofconverted isopentane).

Comparisons between Curves A and B of FIG. 2 and between Curves C and D of FIG. 3 show the importance of the method of the invention. The yield of isopentanc hydroperoxide is in all cases improved for a given conversion rate. Under the same conditions, the production of compounds having the carbonyl function is decreased.

These phenomena do not occur when the amount of 2-methyl 2-butanol is less than about 0.75 per cent of the amount of isopentane introduced, expressed in gram molecules. This lower limit corresponds substantially to the value of the concentration of 2-methyl 2- butanol at the end of the hydroperoxidation reactor when no 2-methyl Z-butanol is introduced into the reaction. lt is known, as a matter of fact, that 2-methyl 2-butanol is a byproductof the reaction of the forma- 20 tion of isopentane hydroperoxide. On the other hand,

peroxide does not increase'beyond an addition of about 8 per cent 2-methyl 2-butanol. A comparison of the representative points of Tests V1 andVlll in FIGS. 2 and 3 shows that the change from an addition of 8 per cent to an addition of 12 per cent of 2-methyl 2-butanol does not bring about any advantage. This is why the preferred range is this case consists of the concentration range of 0.75 per cent to 8 per cent.

EXAMPLE lll This is an example illustrating the method of the present invention wherein tertiary butyl alcohol and 3- methyl 3-pentanol are added, respectively.

The manner of operation is identical to that de scribed in Example I. Tests were carried out, on'the one hand, with the addition of different quantities oftertiary butyl alcohol and, on the other hand, without addition of this alcohol, each resulting pair of tests having indentical conversion rates in both cases. The results of these tests are set forth in Table II.

TABLE 11 Test No.

the addition of quantities of 2-methyl 2-butanol of 50 Tert. butyl alcohol introduced (in mole% of isopentane introduced Reaction Time Converted lh. 50mn w/o addn of ten. butyl alcohol 1h. 50rnn w/o addn of ten. butyl alcohol w/o addn of ten.

alcohol more than 15 per cent is of little. interest, since, on the one hand, it is not advantageous merely from an economic standpoint to add large quantities of anadditive,

Similarly, in Table 111 are set forth the results of tests carried out, on the one hand, with the addition of different quantities of 3-methyl 3-pentanol and, on the other hand, without addition of this alcohol with each and, on the other hand, the yield of isopentane hydro- 55 pair of tests having identical conversion rates.

by adding to the liquid reaction medium tertiary alcohol selected from the group consisting of tertiary butyl alcohol, Z-methyl 2-butanol, Z-methyl 2-butanol, 2- methyl 2-pentanol, and 3-methyl 3-pentanol inan amount between 0.75 per cent and 8 per cent of the total number of gram molecules constituting the liquid reaction medium.

2. A method according to claim 1, wherein the tertiary alcohol is added before the starting of the hydroperoxidation reaction.

3. A method according to claim 1, wherein the tertiary alcohol is added during the hydroperoxidatio'n re- TABLE Ill-Continued Test No. 4 4 5 5' 6 6' Yield of isopentane hydroperoxide (mole% of isopentane Converted) 64.5 58.7 63.0 58.1 64.4 56.2 2-methyl Z-butanol formed (mole% of isopentane convened) 0.7 5.9 0.7 6.0 0.7 6.1 Compounds with carbonyl function formed (mole of isopentane converted) 28.1 30.5 28.4 30.6 28.8 30.9

It is seen that the method of the invention makes it possible to increase the yield of isopentane hydroper- 2O oxide and decrease the yield of 2-methyl 2-butanol and of compounds having the carbonyl function for a given conversion of isopentane. It also makes it possible for a given yield of isopentane hydroperoxide to increase the conversion rate of the isopentane.

We claim 1. ln the method of noncatalyzed synthesis of isopentane hydroperoxide from isopentane in a liquid reaction medium by action of molecular oxygen, the im- 3 provement consisting essentially of hydroperoxidizing O isopentane at a temperature between 100 and 200C action. 

1. IN THE METHOD OF NONCATALYZED SYNTHESIS OF ISOPENTANE HYDROPEROXIDE FROM ISOPENTANE IN A LIQUID REACTION MEDIUM BY ACTION OF MOLECULAR OXYGEN, THE IMPROVEMENT CONSISTING ESSENTIALLY OF HYDROPEROXIDIZING ISOPENTANE AT A TEMPERATURE BETWEEN 100* AND 200*C BY ADDING TO THE LIQUID REACTION MEDIUM TERTIARY ALCOHOL SELECTED FROM THE GROUP CONSISTING OF BUTANOL, 2-METHYL 2-PENTANOL, AND 3-METHYL 3-PENTANOL IN AN AMOUNT BETWEEN 0.75 PER CENT AND 8 PER CENT OF THE TOTAL NUMBER OF GRAM MOLECULES CONSTITUTING THE LIQUID REACTION MEDIUM.
 2. A method according to claim 1, wherein the tertiary alcohol is added before the starting of the hydroperoxidation reaction.
 3. A method according to claim 1, wherein the tertiary alcohol is added during the hydroperoxidation reaction. 